21470778 has 64 divisors (see below), whose sum is σ = 55296000. Its totient is φ = 6048432.

The previous prime is 21470737. The next prime is 21470783. The reversal of 21470778 is 87707412.

It is an unprimeable number.

It is a polite number, since it can be written in 31 ways as a sum of consecutive naturals, for example, 29503 + ... + 30221.

It is an arithmetic number, because the mean of its divisors is an integer number (864000).

Almost surely, 2^21470778 is an apocalyptic number.

It is a practical number, because each smaller number is the sum of distinct divisors of 21470778, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (27648000).

21470778 is an abundant number, since it is smaller than the sum of its proper divisors (33825222).

It is a pseudoperfect number, because it is the sum of a subset of its proper divisors.

21470778 is a wasteful number, since it uses less digits than its factorization.

21470778 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 816 (or 810 counting only the distinct ones).

The product of its (nonzero) digits is 21952, while the sum is 36.

The square root of 21470778 is about 4633.6570870102. The cubic root of 21470778 is about 277.9388527246.

The spelling of 21470778 in words is "twenty-one million, four hundred seventy thousand, seven hundred seventy-eight".